1. Field of the Invention
The present invention relates to urea formaldehyde colloids. The present invention particularly relates to methods of preparing urea formaldehyde polyvinyl alcohol colloids.
2. Background of the Art
Historically, asphalt roofing shingles were made from organic felt mats, principally formed from randomly arranged chopped cellulose fibers that are saturated with a hot asphalt and subsequently formed into asphalt roof shingles. In contrast, for modern applications, wet laid glass fiber mats have replaced the cellulose felt mats which provide increased service life, strength and improved fire resistance.
Unfortunately, fiberglass lacks the natural inter-fiber bonding that is inherent in the natural organic fiber such as cellulose. The chopped glass fibers when randomly disposed in a mat must be bonded together by a suitable binder. The binder adhesively secures crossed glass fibers together contributing to good handling of the mats during processing into fiberglass shingles as well as providing the necessary physical performance properties such as strength, flexibility and long life that is required during roof installation and during the service life of the roof.
As with any commercial concern, when making fiberglass reinforced shingles or any other fiberglass product, it is desirable that useful binders be as cost effective as possible while also having the necessary physical properties. In some aspects, urea-formaldehyde resins are desirable for this application. They are low-cost thermoset materials having a good adhesion, a fast cure rate, desirable mechanical properties, and a lengthy shelf life.
Unfortunately, urea formaldehyde resins without some form of modification may not have sufficient mechanical properties. It has sometimes been observed that fiberglass sheathing prepared with urea formaldehyde resin binders may break during the production of glass mats for the use in the production of shingles. This shortcoming may be overcome however, through the use of water born polymers, such as, emulsion, dispersion and water-soluble polymers. One such waterborne polymer is polyvinyl alcohol.
Polyvinyl alcohol can be readily crosslinked with urea-formaldehyde resin at elevated temperatures to improve mechanical properties of urea-formaldehyde-based binder and also improve water resistance. However, urea-formaldehyde resin and polyvinyl alcohol water solution form a two-phase system due to immiscibility or limited compatibility, depending on the molecular weight (MW), degree of hydrolysis of polyvinyl alcohol, and solid content of the formulation. Currently, it is customary in the art of making polyvinyl alcohol resin, that less than 1% by weight, is mixed with urea-formaldehyde resin to enhance the urea-formaldehyde resin performance or add the small amount of urea-formaldehyde resin into polyvinyl alcohol solution to improve polyvinyl alcohol water resistance in commercial products. It would be desirable in the art to be able to increase the amount of polyvinyl alcohol introduced into a urea formaldehyde resin to improve its performance as a binder.